A scanner is a computer peripheral that when presented with an image, produces a scanner output signal for use by digital electronic equipment, such as a computer. Prior to operating on the graphic information conveyed by the scanner output signal (for example, cropping, sizing, etc.), the equipment or computer usually creates a file for storing the graphic information as it is produced.
The smallest element of a graphic image as scanned (or as used by a computer) is called a pixel, short for picture element. A scanner output signal describes the color and brightness of each pixel in each horizontal line scanned across the image. Each line is called a scan line. Because a scan line is ordinarily one pixel thick in the vertical direction, the scanner output signal describes hundreds of scan lines, each a minute vertical distance along the image until the full image has been reported.
Small pixel dimensions provide for high resolution scanning, yet high resolution raster signals tend to require large files for retaining information about an enormous number of pixels. A smaller file can be produced when redundant information provided by the scanner output signal is removed by conventional data compression algorithms.
Unfortunately, conventional data compression algorithms exhibit an unpredictable delay in compressing the scan signal from a particular image. Complex images require more data compression time due to many changes in pixel intensities. Because not all images are complex, system throughput is slowed when images are input to a scanner with intervening delay of a prescribed maximum time.
A scanner operator may be required to present an image more than once due to incomplete or undesirable scanned results. For example, when a sequence of complex images is presented, loss of scanned data may occur. In such a case the operator must make repeated attempts to scan the offending image and often repeat scanning of some or all of the images following it. Operator intervention to reattempt scanning may also be required when an image is not in proper orientation, when an exposure of the image needs to be adjusted for contrast or color, when an image is misaligned, or when the image is incomplete as when a page fold covers part of an image.
In view of the problems described above and related problems, the need remains for systems for monitoring scanning processes and for methods for processing pixels for display and storage.